This invention relates, in general, to a cooling module for an electronic control unit and, more particularly, to an integrated cooling module for an electronic control unit, wherein the integrated cooling module cools the electronic module using convection and conduction.
Engine mounted electronic control units for diesel engines are subject to a high level of heat and vibration and their performance is often limited or impaired due to these conditions. Typically, in order to reduce the high level of heat and enhance thermal performance, traditional cooling methods such as the use of an external cooling plate or the use of a separate external fuel cooler, are implemented. However, traditional cooling methods are often not the most effective means for cooling electronic control units. For example, in a direct engine mount application where a Polybent(trademark) printed circuit board, that is a printed circuit board that has a flexible circuit that is bent, is used for packaging an electronic control unit, an external cooling plate would not the most effective method for cooling the electronic control unit. In a Polybent(trademark) printed circuit board, a printed circuit board is essentially folded in half, forming a u-shaped printed circuit board consisting of two main partitions facing each other. The two main partitions are connected to each other by a flexible circuit. One of the two main partitions is mounted near the engine block, leaving the second main partition to be mounted away from the engine block. Typically, in a Polybent(trademark) printed circuit board, the external cooling plate can only enhance the heat dissipation of one main partition in between the control unit and the engine block. Therefore, heat dissipating components on the other main partition do not directly benefit from the presence of an external cooling plate and consequently the electronic control unit will not dissipate heat efficiently.
The presence of an external cooling plate is disadvantageous to the structural integrity of the electronic control unit having a Polybent(trademark) printed circuit board, because the mass and stiffness of the external cooling plate amplifies the excitation signal originated from the engine block on which the electronic control unit is mounted to. Additionally, by the nature of design and functionality, the structural rigidity of an external cooling plate is similar to the structural rigidity of a Polybent(trademark) printed circuit board, which in turn causes additional amplification of the excitation signal originating from the engine block due to a coupling effect.
Electronic control units that are not manufactured using a Polybent(trademark) printed circuit board, but rather, are manufactured in a conventional manner using a flat printed circuit board, still have many limitations with traditional cooling methods. For example an external cooling plate or a separate external fuel cooler are all traditional cooling modules in which the thermal performance of the device depends on how well the device is mounted onto the electronic control unit. Since these traditional cooling modules rely on conductive heat transfer, they must come into direct contact with the surface of the electronic control unit that they are cooling. Variations within manufacturing processes limit the amount of contact that can be made between electronic control unit and these traditional cooling modules. Moreover, these traditional cooling modules subject the electronic control unit to increased vibration levels. These increased vibration levels cause intermittence in the contact area between the cooling module and the electronic control unit that impairs the cooling efficiency of the traditional cooling module. Further, as mentioned earlier, traditional cooling modules are not optimized for Polybent(trademark) printed circuit boards.
Another device that can be used for cooling an electronic control unit is an integral backside cooling module. Backside cooling modules include a five-sided cast aluminum housing with copper tubing inserted into the cast aluminum housing during the molding process. The electronic control unit is then mounted to the housing using screws and the device uses conduction to remove the heat from the electronic control unit. Again backside cooling modules suffer similar problems as the traditional cooling modules in that they both use conductive heat transfer to cool the electronic control unit. Conductive heat transfer requires the cooling module to be in constant contact with the electronic control unit, a requirement that is very difficult to achieve with engine mounted electronic control units due to the harsh vibration levels incurred, as discussed above. Moreover, using copper tubing inserted into a cast aluminum housing is very risky since material mismatches will result in the device failing to cool the electronic module.
Accordingly, further development of cooling modules for cooling an electronic control unit, and more specifically, for cooling an electronic control unit mounted to an engine block, is necessary in order to increase and enhance heat dissipation efficiency of an electronic control unit.